No, there is no "unzip" function available. The reason for that is that creating a simple zip file is much easier than unzipping a zip file. madZip is built in such a way that is just does whatever is necessary to create a simple zip file. madZip doesn't even support all the funny compression formats the ZIP format can handle. So if you tried unzipping a zip archive with madZip, there'd be some zip files that simply wouldn't unzip at all.